High gain omniazimuth antenna



Jan. 2%, 1959 L. HATKIN 2,871,477

HIGH GAIN OMNIAZIMUTH ANTENNA Filed'May 4, 1954 INVENTOR. LEONARD HATKJN ifitates Pa HIGH GAIN OMNlAZlMUTH ANTENNA Leonard Hatkin, Elberon, N. J., assignor to the United States of America as represented by the Secretary of the Army The invention described herein may be manufactured and used by or for the Government for governmental purposes, without the payment of any royalty thereon.

This invention relates to antenna systems and more particularly to an omniazimuth reflector-type antenna system.

In many radar systems, especially beacons and navigational aid systems, it is desirable to provide an omniazimuth radiation pattern with the energy concentrated in a narrow elevation beam. Heretofore this was accomplished by utilizing stacked antenna arrays which are known to be frequency sensitive and usually require a complicated phasing arrangement for feeding the antennas.

It is therefore an object of the present invention to provide an improved ornniazimuth antenna system overcoming these limitations.

It is another object of the present invention to provide a high gain reflector-type omniazimuth antenna system for producing a relatively narrow elevation beam having an improved signal-to-noise ratio.

In accordance with the present invention there is provided an omniazimuth antenna system comprising a reflector having a surface of revolution formed by rotating a portion of a parabola about its latus rectum. The peripheral surface of the reflector comprises a plurality of spaced longitudinal conducting members each disposed at 45 degrees with respect to the latus rectum at the respective points of intersection of the axis of the rotated parabola and the members at the vertex, and having a common focus. The members go around the peripheral surface in one direction such that diametrically opposed members are disposed 96 degrees relative to each other. Means are included at the focus for producing a resultant radiation pattern polarized 45 degrees with respect to the latus rectum whereby the reflected radiated energy from each of said members passes through the reflector at respective points 180 degrees from the reflecting members.

For a better understanding of this invention together with other and further objects thereof, reference is had to the following description taken in connection with the accompanying drawings in which:

Figure 1 is a perspective drawing of the antenna system embodying my invention;

Figure 2 shows the parabola which forms the surface of revolution for the reflector shown in Figure 1;

Figure 3 is an explanatory diagram showing the relationship between antenna feed current vectors, and

Figure 4 illustrates a waveguide type antenna for use at relatively high frequencies.

Referring now to Figures 1 and 2 of the drawing, there is shown at 19 an antenna reflector having a surface of revolution formed by rotating a portion of a parabola about its latus rectum. In Figure 2 there is shown a parabola 12 having a vertex 14, a focus 16, and a latus rectum 18 which is a chord through focus 16 perpendicular to the axis 29. The peripheral surface of reflector is formed by rotating parabola 12 axially about latus Patented Jan. 27, 1959 rectum 18 so that the locus of the vertex of the rotated parabola comprises a circle, indicated by the dashed line 22 in Figure 1, in a plane perpendicular to the latus rectum and having the focus 16 at its center. The loci of the end points 24 and 26 of parabola 12 are circles concentric with vertex locus circle 22 and are shown in Figure 1 as metallic annular rings 28 and 30 respectively. The peripheral surface of revolution comprises spaced longitudinal conducting members 32 connected intermediate annular rings 28 and 30. The members 32 are arranged so that they each intersect the vertex locus circle 22 at an angle of 45 degrees with respect to the latus rectum so that, as the members 32 go around the peripheral surface of revolution in one direction, any two of these members which interset the vertex locus circle 22 at respective diametrically opposite points are displaced degrees relative to each other. In Figure 1, two such members are shown respectively at 32' and 32". Thus, for any one conducting member 32' there is a corresponding member 32" displaced 90 degrees relative to said one member.

Centrally positioned within reflector 10 at the common focus 16 is a feed antenna system shown in Figure 3 comprising a horizontally polarized loop antenna 34 and a vertically polarized dipole antenna 36 aligned with the latus rectum. These feed antennas are so phased that the resultant current vector originating at the focus 16 produces an omniazimuth radiation pattern polarized 45 degrees with respect to the latus rectum 18. Such a pattern can readily be produced by feeding to the antennas a predetermined ratio of radio-frequency energy 90 degrees out of phase. It is to be understood of course that at high frequencies suitable well known waveguide antenna arrangements may be utilized to produce this radiation pattern. One such arrangement, shown in Figure 4, may comprise a circular waveguide 29 simultaneously operating in the TM and TE modes and utilizing a suitable splash reflector 31 to properly direct the radiated energy to the members 32. The TE and TM modes will produce identical doughnut-shaped patterns but with orthogonal polarization. The two modes are adjusted in phase and amplitude so that 45 polarization of the resultant field is produced. With either feed antenna system arrangement the resultant current vectors at any two diametrically opposite points are displaced 90 degrees relative to each other. This is clearly shown in the vector diagrams shown in Figure 3. The horizontally polarized vectors at diametrically opposite points are indicated by H and 1-1 respectively, and the vertically polarized vectors are indicated by V and V respectively. Assuming equal energy being radiated by both the loop antenna and the dipole antenna, then obviously the respective resultant vectors R and R will be disposed 45 degrees with respect to the vertical dipole antenna but displaced 90 degrees relative to each other. For purposes of explanation, it may be assumed that resultant vector R is parallel to member 32 and resultant vector R is parallel to member 32". Hence energy striking members 32' and 32 respectively will produce collimated rays of energy reflected along a diametric plane of the reflector. On reaching the respective opposite sides of the reflector, the reflected energy will pass through unobstructed since the respective opposite reflecting members are at 90 degrees to the polarization of the radiation. The net result is an omniazimuth radiation pattern polarized 45 degrees with respect to the vertical and concentrated in a narrow beam of elevation.

An arc of a circle may be substituted for the parabola to form the surface of revolution provided, of course, that the curvature of the arc is chosen to produce a minimum of aberration. In such an arrangement members 32 will have an arcuate contour.

While there have been described what are at present considered to be the preferred embodiments of this invention, it will be obvious to those skilled in the art that various changes and modifications may be made therein without departing from the invention and it is, therefore, aimed in the appended claims to cover all such changes and modifications as fall within the true spirit and scope of the invention.

What is claimed is:

1. An omniazimuth antenna system for producing a narrow beam in elevation comprising a reflector having a surface of revolution formed by rotating a parabola about its latus rectum in such a manner that the locus of the vertex of the parabola as it is rotated comprises a circle in a plane perpendicular to the latus rectum and a common focus at the center of said circle, said surface comprising a plurality of spaced longitudinal conducting members each disposed 45 degrees with respect to said latus rectum at the respective points of intersection of the vertex circle locus and said members, said members going around said surface in one direction so that any two members intersecting the vertex circle locus at respective diametrically opposed points are displaced 90 degrees relative to each other, and incident radiation means at said focus for producing a resultant omniazimuth radiation pattern polarized 45 degrees with respect to said latus rectum whereby the reflected radiated energy from each of said members passes through said reflector at respective points diametrically opposite the reflecting members.

2. An omniazimuth antenna system for producing a narrow beam in elevation comprising a reflector having a peripheral surface formed by rotating a portion of a parabola having a predetermined focus about its latus rectum, said surface comprising a plurality of longitudinally spaced conducting members each disposed 45 degrees with respect to the latus rectum at the point of intersection of the vertex of the rotated parabola and each of said members as the members go around said peripheral surface in one direction, and incident radiation means at said focus for producing a resultant 'omniazimuth radiation pattern polarized 45 degrees with respect to said latus rectum whereby the radiated energy reflected from each of said members passes through said reflector at respective points 180 degrees from the reflecting members.

3. The antenna system in accordance with claim 2 wherein said last mentioned means comprises a dipole antenna polarized in the direction of said latus rectum and a loop antenna polarized in a direction perpendicular to said latus rectum.

4. An omniazimuth antenna comprising a horizontally polarized loop antenna, a vertically polarized dipole antenna centrally positioned within said loop antenna, means for exciting said antennas to produce a resultant omniazimuth radiation pattern polarized degrees with respect to the longitudinal axis of said dipole antenna, means circumferentially encompassing said antennas for reflecting the resultant radiation to produce collimated rays of reflected radiation, the circumferential periphery of said reflecting means comprising a plurality of spaced longitudinally bowed conducting members having a common focus at the origin of said radiation pattern and having respective vertices disposed in a circle with said focus at its center, said circle being in a plane perpendicular to said dipole antenna, said members being disposed 45 degrees with respect to said dipole antenna at the vertices.

5. An omniazimuth antenna system for producing a narrow beam in elevation comprising a reflector including spaced axially aligned annular rings, a plurality of spaced longitudinal parabolically bowed conducting members interconnecting said rings and having a common focus, the locus of the vertices of said members being a circle coaxial with said rings, each of said members being disposed 45 degrees with respect to the axis of saidrings at said vertices as the members go around said rings in one direction so that each member and its respectively diametrically opposed member are displaced degrees relative to each other, and incident radiation means positioned at said focus for producing an omniazimuth radiation pattern polarized 45 degrees with respect to said axis whereby the reflected radiated energy from each of said members passes through said reflector at respective points diametrically opposite the reflecting members.

References Cited in the file of this patent UNITED STATES PATENTS Rung Dec. 27, 1932 Wheeler Aug. 12, 1947 Iams May 30, 1950 

